For some years, laser welding has proven to be an attractive joining technique for microfluidic devices made of thermoplastic materials.
This involves, for example, one thermoplastic component, which has a depression acting as a microchannel, incorporating a laser absorber and being welded to another thermoplastic component by exposure to a laser beam. However, for reasons of adjustment, it is not possible to take the weld seam exactly flush along the depression opening. Moreover, the volume of the depression may be changed if the weld seam runs directly along the depression opening.
The publication US 2004/0053237 A1 describes the production of a microfluidic device by arranging a mask layer, which has apertures for forming microchannels, between two substrates and connecting the arrangement by means of laser welding, the weld seam being formed at a distance from the microchannels.
However, a weld seam formed by a conventional method at a distance from the microfluidic chambers may have the effect that capillaries form between the substrates and, if applicable, the mask layer in the region between the weld seam and the microchannels. Capillary formation along a microchannel is problematic, however, for many microfluidic applications.